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About RAM Speeds and CL

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  • About RAM Speeds and CL

    I figured this was the best place to ask since it specializes in memory.

    I been trying to choose DDR4 for a bit now, but I'm not sure what the real increase would be with faster speeds. I plan to be working with Zbrush, Maya, FumeFX, Unreal Engine 4, basically 3D applications. I'd be working with 32GB for now on a dual channel, not sure if all of this matters. I was wondering if two or four sticks had any impact in performance and what would be the real differences between 2133 14 CL, 2800 CL 14, 2800 C16, or even 3200 14, 3200 16 would be noticeable beyond benchmarks.

  • #2
    The impact isn't enormous. You can step up the RAM speed 20%, but only get a few percent in overall system gain.
    If you can't run the actual benchmarks, you can get a rough indication of performance by dividing the bandwidth by the latency.
    Bandwidth Latency Score
    2133 14 152.4
    2800 14 200.0
    2800 16 175.0
    3200 14 228.6
    3200 16 200.0
    So 3200CL14 will be slightly better than 2800CL14. The more channels the better, it allows interleaving and thus higher bandwidth. If you have a CPU that does 4 channels, then get 4 sticks. Otherwise get the 2 sticks. There is no advantage in using 4 sticks rather than 2 when the CPU only have dual channels. Leaving 2 slots empty give you an upgrade path.

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    • #3
      Originally posted by David (PassMark) View Post
      The impact isn't enormous. You can step up the RAM speed 20%, but only get a few percent in overall system gain.
      If you can't run the actual benchmarks, you can get a rough indication of performance by dividing the bandwidth by the latency.
      Bandwidth Latency Score
      2133 14 152.4
      2800 14 200.0
      2800 16 175.0
      3200 14 228.6
      3200 16 200.0
      So 3200CL14 will be slightly better than 2800CL14. The more channels the better, it allows interleaving and thus higher bandwidth. If you have a CPU that does 4 channels, then get 4 sticks. Otherwise get the 2 sticks. There is no advantage in using 4 sticks rather than 2 when the CPU only have dual channels. Leaving 2 slots empty give you an upgrade path.
      Ahhh thank you. I see the only big upgrades are leaps rather than steps and this will help my decision. I'll be sure to perform a bench once everything is setup.

      Sadly it is a z170 chip, so only dual channel. Used to hear that a 4 vs 2 DIMM configuration would result in a performance loss, but I wasn't sure how it would since it'd be dual channel either way or how it really affects the IMC. Still have only the general idea of how RAM functions.

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      • #4
        There are some deep technical arguments about subtle timing differences that you can get with 4 vs 2 sticks. And some arguments around which is the most stable & reliable. But the net differences are so small that for 99.9% of users they'll never notice the difference at the application level.

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